BBB wireless wifi disconnects after ~20 -30 mins

Hi All,
I am not sure if anyone else has faced this issue. I have BBB Wireless installed with latest Debian installed in it. Wifi works fine for less than an hour and disconnects. I use Dynamic IP. Can you suggest me some solution for my problem?

More details:

/boot/uEnv.txt

#Docs: http://elinux.org/Beagleboard:U-boot_partitioning_layout_2.0
uname_r=4.4.91-ti-r133
#uuid=
#dtb=
###U-Boot Overlays###
###Documentation: http://elinux.org/Beagleboard:BeagleBoneBlack_Debian#U-Boot_Overlays
###Master Enable
#enable_uboot_overlays=1